Most of these dishes are relatively simple, but the exact flavouring / amount of chilli is what makes it.
I would guess (!)
Stir fry the chicken until just coloured, add chopped chillies (not de-seeded) and fry some more.
Add (optional) onion / mushroom / peppers if you want, finally add garlic but don't overcook now or it will go bitter.
Then just add as much soy (or oyster) sauce, or both, as you like, heat through and thats it.
Most stir fry dishes are that easy. Enjoy.